Ultrasensitive immunosensor for acrylamide based on chitosan/SnO2-SiC hollow sphere nanochains/gold nanomaterial as signal amplification.

An electrochemical immunosensor for ultrasensitive detection of acrylamide (AA) in water and food samples was developed. SnO2-SiC hollow sphere nanochains with high surface area and gold nanoparticles with good electroconductivity were fabricated onto the surface of a glassy carbon electrode pre-coated with chitosan. The coating antigen (AA-4-mercaptophenylacetic acid-ovalbumin conjugate, AA-4-MPA-OVA) was immobilized on the electrode. Polyclonal antibody specific for AA-4-MPA was conjugated to gold nanorod (AuNR) as primary antibody (AuNR-Ab1). Horseradish peroxidase labelled anti-rabbit antibody produced in goat was conjugated to AuNR as secondary antibody (HRP-AuNR-Ab2). For detection, the analyte (AA-4-MPA) in sample competed with coating antigen for binding with AuNR-Ab1. After washing, HRP-AuNR-Ab2 was added to capture the AuNR-Ab1, and the electrical signal was obtained by addition of hydroquinone and H2O2. After investigation of the binding ability on nanomaterials and optimization of competitive immunoassay conditions, the proposed immunosensor exhibited a sensitive response to AA with a detection limit of 45.9 ± 2.7 ng kg-1, and working range of 187 ± 12.3 ng kg-1 to 104 ± 8.2 μg kg-1 for drinking water samples. Recoveries of AA from spiked samples were ranged from 86.0% to 115.0%. The specificity, repeatability and stability of the immunosensor were also proved to be acceptable, indicating its potential application in AA monitoring.